1. Field of the Invention
THIS INVENTION relates to improvements in concrete keyed joints.
2. Prior Art
Because concrete undergoes thermal expansion and contraction, it is necessary to provide expansion joints or breaks in concrete slabs, footpaths and the like to at least minimise unwanted cracking in the concrete. For example, it is common practice to provide expansion joints or break lines every 1.0 to 1.5 meters along footpaths.
Keyed jointing systems have been proposed and one system is sold under the "TOBY" trade mark. While this system is preferable to laying the concrete in spaced sections and then laying the concrete in the intermediate sections separately, the system has a number of deficiencies. It is difficult to accurately align the stakes before the joint plates are positioned. If the stakes or plates are disturbed, e.g. by being stepped on by the labourers, realignment of the stakes and plates is difficult. Thirdly the joint plates must be crimped into engagement with the tops of the stakes and only the upper portions of the joint plates are anchored by the stakes until the concrete is poured. Finally, a removable cap must be removed when the concrete has at least partially set to leave the required break line.